Grate



VSept- 17,1957 H. L. WAGNER 2,806,439

GRATE Filed Nov. 8, 1952 United States Patent O GRATE Herbert L. Wagner, Detroit, Mich., assignor to Detroit Stoker Company, Detroit, Mich., a corporation of Michigan This invention relates to furnace grates and, more particularly, to an improved continuous cleaning furnace grate adapted for use in a furnace having a spreader type fuel stoker.

In furnaces of this type, a Stoker is usually provided adjacent the front of the furnace which has a plurality of rotating blades which propel coal particles evenly onto the grate with the heavy or large particles being projected farther back into the furnace. Air is supplied under pressure to the underside of the grate and ows upwardly through the grate to support the combustion of the coal on the grate, as well as the combustion of coal particles in suspension adjacent the front of the grate. The grate is provided with overlapping, stationary and movable grate bars which reciprocate relative to each other so as to convey the burning coal forwardly to the front of the furnace where the ashes are dropped into an ash pit adjacent thereto. However, prior grates have not been entirely satisfactory, in that the individual grate bars are supported at the front and rear ends thereof over their entire widths, and as they are commonly rough castings, any warping or twisting thereof, due to the heat Within the furnace causes them to cock so that an opening'appears between the lower surface of the grate bars and the adjacent surface on which they rest. Such openings cause an excessive air leakage through the grate which seriously upsets the ash and fuel bed conditions and causes a high rate of ow of excess air in the furnace.

Accordingly, an object of the present invention is to overcome disadvantages inherent in such furnace grates and to provide an improved grate having sealing means adapted to prevent leakage of excess air through the grate.

Another object of the invention is to provide improved grate bar supporting means which automatically compensates for warping or twisting of the grate bars, and prevents the formation of openings 'Between the overlapping portions of the bars.

Another object of the invention is to provide an improved grate arrangement that is simple in construction, economical of manufacture, durable, etlicient and reliable in operation.

Another object of the invention is to provide an improved grate arrangement on which a greater variety of bituminous coal may be burned more eiiciently than was heretofore possible.

Still another object of the invention is to provide an improved furnace grate, adapted for use with a spreader v type stoker, having simple and efficient means for obtaining maximum burning etlciency and maximum grate cleanliness.

Yet another object of the invention is to provide an improved furnace grate that may be readily adapted vfor* installation in furnaces of various sizes,

With the above as well as other and in certain cases more detailed vobjects in view, which will become apparent from the following description and the appended claims, a'preferred but illustrative embodiment of the invention is illustrated in the accompanying drawing, throughout the several views of which corresponding reference characters designate corresponding parts and wherein:

Fig. l is a longitudinal, sectional view of a portion of a furnace embodying the grate construction of the present invention;

Fig. 2 is an enlarged, side elevational view `of an individual grate bar;

Fig. 3 is a sectional view of the structure illustrated in Fig. 2 taken substantially on the line 3-3 of Fig. 2;

Fig. 4 is a sectional view taken substantially on the line 4 4 of Fig. 1 and Fig. 5 is a perspective view of a portion of the assembled grate, with portions broken away for purposes of clarity.

Referring to the drawing, and more particularly to Fig. 1, a furnace 10 is illustrated which includes the usual walls 12, formed of rebrick or the like, and supporting structure 14. The furnace also includes a combustion chamber 16 in which the fuel, such as coal, is burned, the hot gases passing up through the furnace to heat the boiler and/or heating system, as the case may be. The ash or less combustible portions of the fuel remain on the grate 18 which is disposed adjacent the bottom of the combustion chamber, and is constructed according to the present invention, as will be hereinafter described in greater detail.

A spreader type Stoker (not shown) is secured to the box girder 20 attached to the front wall of the furnace adjacent the front portion of the grate 18. The Stoker feeds the fuel into the furnace and onto the grate, spreading the fuel uniformly on the grate, both longitudinally and laterally. The heavier or larger particles are projected onto the rear portion of the grate while the smaller particles fall onto the grate forwardly thereof, or are burned in suspension above the front portion of the grate. In order to facilitate the burning of the lighter particles in suspension, air is supplied through a plenum chamber 22 formed by the box girder 20, the air passing through the passageway 24 to float the fine particles of fuel into the furnace.

When the furnace is in operation and the fuel is being delivered from the stoker onto the grate, the combustible part of the fuel is converted into hot Igases which pass upwardly through the furnace, a boiler and/or fuel heating system and the less combustible parts of the fuel remain on the grate. As the process of combustion continues, the depth of the ash will increase on the grate and the rate of increase is directly proportional to the amount lof fuel burned per square foot per hour and the percentage of ash in the fuel being burned. The grate 18 serves two functions. It acts, first, as a grate for burning the fuel and, secondly, as a conveyor for carrying the ash out of the furnace and into an ash pit 26, adjacent the front end of the grate. According to the present invention, the grate 18 is formed Vof a plurality of overlapping sections or bars 30 and 32. Alternate bars 30 are stationary while movable bars 32 are provided between adjacent stationary bars. The front ends of the movable bars 32 overlap the rear or back ends of the stationary bars while the front ends of the stationary bars overlap the rear or back ends Iof the movable bars. Movable bars 32 are reciprocable relative to the stationary bars 30 and reciprocate from front to rear relative to the furnace or `from left to right in Fig. l.

As shown in Fig. 2, the upper porti-on 34 of each movable grate bar 32 is substantially iat and an integral, centrally disposed, downwardly extending web portion 36 is provided which extends longitudinally of the bar, While integral, spaced, downwardly extending web portions 38 extend transversely of the bar. Spaced air ports or openings, such as 40, are provided in the flat portion 34 through 'which air lows to support the combustion of the fuel.

more eicient combustion of the fuel is obtained than was heretofore possible.

While a preferred embodiment of the invention has been shown and described, it will be understood that various changes and modifications may be made without departing from the spirit and scope-of the invention.

What is claimed is:

1. A furnace grate arrangement comprising a plurality of alternate stationary and movable members, each of said movable members having one end portion thereof overlapping the adjacent stationary member, support means making substantially point contact with the other end portion of each of said members and permitting free rocking movement of said members whereby said members are free to rock to maintain said one end portion of each of said members in sealing relationship with respect to the adjacent member, and means for reciprocating said movable members relative to said stationary members.

2. A furnance grate arrangement comprising a plurality of alternate stationary and movable members, the forward end portion of each of said movable members overlapping the rear end portion of the adjacent stationary member, support means making substantially line contact in a longitudinal direction relative to said movable members with the rear end portion of each of said members and permitting free rocking movement of said members whereby said members are free to pivot to maintain said one endvportion of each of said members in sealing relationship with respect to the adjacent member, and means for reciprocating said movable members relative to said stationary members.

3. In combination, a plurality of movable and stationary grate bars, each of said bars having a triangularly sectioned portion extending downwardly from the top portion thereof, the front portion of each of said movable bars overlapping the rear portion of the adjacent stationary bar, support means abutting the apex of said triangularly sectioned portion of each of said bars whereby said members are free to pivot to maintain the forward end portions thereof in sealing relationship with respect to the adjacent member, and means for reciprocating said movable bars.

4. A furnace grate arrangement comprising a plurality of stationary and movable members, the forward portion of each of said movable members overlapping the rear portion of the adjacent stationary member, a sealing element having an upwardly extending rib portion interposed between each of said overlapping portions, the forward portion of each of said movable and stationary members being provided with a transverse groove adapted to receive said upwardly extending rib portion whereby relative sliding movement is permitted between each of said members and said sealing element in a direction perpendicular to the plane of the lower surface of the sealing element, each of said movable and stationary members having a triangular depending portion adjacent the rear end thereof, means effecting substantially line contact i with the apex of said depending portion of each of said movable and stationary members whereby said movable and stationary members are free to pivot to maintain the forward portions thereof in sealing relationship with respect to the adjacent sealing element, and means for reciprocating said movable members relative to said stationary members.

5. In combination, a plurality of movable and stationary grate bars, each of said bars having a substantially ilat top portion and a centrally'disposed, triangularly sectioned portion extending downwrdly from said top portion at a position near, but spaced from, the rear end thereof, the front portion of leach of said movable bars overlapping the rear portion of the adjacent stationary bar, a sealing element having `an upwardly extending rib portion interposed between each of said overlapping portions, the forward portion of each of said bars being provided with a transverse stepped groove adapted to receive said upwardly extending rib portion whereby relative sliding movement is permitted between eachof said bars and said sealing element in a direction perpendicular to the plane of the lower portion of the sealing element, means abutting the apex of said triangularly sectioned portion for supporting the rear portion of each of said bars whereby said bars are free to pivot to maintain the forward end portions thereof in sealing relationship with respect to the adjacent sealing element, `and means for moving said movable bars longitudinally with respect to said stationary bars.

References Cited in the le of this patent UNITED STATES PATENTS 540,669 Ingram et al. June 1l, 1895 l 689,827 McClave Dec. 24, 1901 1,111,059 Dietz Sept. 22, 1914 1,817,484 Goebel Aug. 4, 1931 1,908,992 Martin May 16, 1933 2,250,067 Martin July 21, 1941 FOREIGN PATENTS 369,015 Great Britain Mar. 17, 1932 

